The present invention is related to a laminate containing a fibrous layer and a film layer. More particularly, the present invention is related to a liquid barrier laminate that is bulked and dimensionally stabilized.
Various disposable articles, e.g., diapers, training pants, protective garments, drapes, and feminine and incontinence care products, that contain an outer layer of a liquid impervious or barrier material are widely available. The outer layer of these articles is typically produced from a thermoplastic film. Although a film layer may provide the needed liquid barrier property, the film layer does not tend to provide desirable textural and visual properties.
One commercially useful approach in solving the textural and visual disadvantages is imparting a cloth-like texture on the outside of the film layer. For example, the desired texture can be imparted by laminating a nonwoven fabric adhesively or thermally on a film layer. U.S. Pat. No. 4,725,473 to Van Gompel et al. discloses, for example, a liquid impervious composite that is produced by depositing an unbonded nonwoven layer onto a film layer and then thermally bonding the composite. Alternatively, a bonded nonwoven fabric can be placed in juxtaposition with a film and then bonded to form a composite. These composites having soft, cloth-like textural properties are highly useful outer cover materials for various garments, such as diapers, training pants, incontinent garments and the like, although the textural properties of these composites may not be as pleasing as some natural fiber fabrics.
Additionally, although these composites are suitable for various uses, the composite may not be thermally stable since the layers, especially the film layer, tend to shrink and deform when exposed to a temperature above the softening temperature of the polymer or polymers forming the composite. It has been proposed that the film layer should be thermally annealed, to ameliorate the shrinkage problem, and then formed into the composite. Even though this annealing process provides a thermally stabilized composite, the texture and hand of the composite can be further improved.
There remains a need for further improving tactile properties and thermal stability of liquid resistant composites.
The present invention provides a process for producing a three dimensionally texturized liquid resistant laminate having a fibrous nonwoven layer and a liquid resistant layer, wherein the liquid resistant layer has a higher latent shrinkability than the nonwoven layer. The process has the steps of placing the fibrous layer and the liquid resistant layer in juxtaposition to form a laminate, attaching the fibrous layer and the liquid resistant layer at a plurality of spaced-apart bond locations, heating the bonded laminate to a temperature that activates the latent shrinkability of the liquid resistant layer, and allowing the heated laminate to retract such that the liquid resistant layer shrinks and said fibrous layer forms gathers between said bond locations, thereby forming a three dimensional texture and heat annealing the laminate.
The invention additionally provides a three dimensionally texturized laminate having a fibrous layer and nonelastic liquid resistant layer. The layers of the laminate are joined at a multitude of spaced-apart bond sites, and the laminate is heat annealed, wherein the fibrous layer forms gathers between spaced-apart bond sites to provide the three dimensional texture and the laminate has a liquid resistant layer to fibrous layer length ratio between about 0.7 and about 0.95.
The term xe2x80x9cnonelasticxe2x80x9d as used herein refers to any polymeric material which, upon application of a stretching force, is not recoverably stretchable to a stretched, biased length which is more than 125% of its original unbiased length, and the term xe2x80x9crecoverablexe2x80x9d refers to a contraction of more than 40% of its stretched length upon release of the stretching force. The term xe2x80x9cspunbond fiber nonwoven webxe2x80x9d refers to a nonwoven fiber web of small diameter filaments that are formed by extruding a molten thermoplastic polymer as filaments from a plurality of capillaries of a spinneret.
The extruded filaments are cooled while being drawn by an eductive or other well-known drawing mechanism. The drawn filaments are deposited or laid onto a forming surface in a generally random, isotropic manner to form a loosely entangled fiber web, and then the laid fiber web is subjected to a bonding process to impart physical integrity and dimensional stability. The production of spunbond webs is disclosed, for example, in U.S. Pat. No. 4,340,563 to Appel et al., U.S. Pat. No. 3,802,817 to Matsuki et al. and U.S. Pat. No. 3,692,618 to Dorschner et al. Typically, spunbond fibers have an average diameter in excess of 10 xcexcm and up to about 55 xcexcm or higher, although finer spunbond fibers can be produced. The term xe2x80x9cstaple fibersxe2x80x9d refers to discontinuous fibers, which typically have an average diameter similar to or somewhat smaller than that of spunbond fibers. Staple fibers are 30 produced with a conventional fiber spinning process and then cut to a staple length, from about 1 inch to about 8 inches. Such staple fibers are subsequently carded or air-laid and thermally bonded to form a nonwoven web. The term xe2x80x9cmeltblown fiber webxe2x80x9d or xe2x80x9cmelt-spray fiber webxe2x80x9d indicates a fiber web formed by extruding a molten thermoplastic polymer through a spinneret containing a plurality of fine, usually circular, die capillaries as molten filaments or fibers into a high velocity gas stream which attenuates or draws the filaments of molten thermoplastic polymer to reduce their diameter. In general, meltblown fibers have an average fiber diameter of up to about 10 xcexcm, although thicker meltblown fibers can be produced. After the fibers are formed, they are carried by the high velocity gas stream and are deposited on a forming surface to form an autogenously bonded web of randomly dispersed, highly entangled meltblown microfibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin. The term xe2x80x9cflashspun fiber webxe2x80x9d indicates a nonwoven fabric formed by spraying a high temperature, pressurized solution of fiber-forming polymer and a volatile solvent into a low-temperature and pressure environment to rapidly evaporate the solvent. Such process provides autogenously bonded microfiber nonwoven webs and is, for example, disclosed in U.S. Pat. No. 3,169,899 to Steuber. The term xe2x80x9chydroentangled fiber webxe2x80x9d indicates a nonwoven fabric of continuous or staple fibers that are consolidated and entangled by streams of liquid jet. Hydroentangled nonwoven fabrics of staple length fibers and continuous filaments are disclosed, for example, in U.S. Pat. No. 3,494,821 to Evans and U.S. Pat. No. 4,144,370 to Bouolton.